1. Field of the Invention
The present invention generally relates to electric power tools. More particularly, the present invention relates to circular saws including a base plate, a saw blade assembly mounted on the base plate, and a lower blade guard for covering the lower portion of the saw blade.
2. Description of the Related Art
A typical circular saw includes a generally rectangular base plate and a saw blade assembly mounted on the base plate. The assembly in turn includes a motor-driven circular saw blade protruding below the base plate with the lower portion or teeth of the blade covered by a rotatable lower blade guard. Additionally, an extension spring is stretched between a portion of the blade guard decentered or displaced from the axis of its rotation and the saw blade assembly at a suitable location. Under normal conditions (or when the saw is not used), the lower blade guard is rotated to its closed position by the biasing or tensile force exerted by the extension spring, thus covering the teeth of the saw blade. Conversely, to cut a workpiece, the front end of the lower blade guard is first brought into abutment with a workpiece and the tool is moved in the direction in which the cutting is to progress. The guard is then manually retracted against the biasing force of the extension spring so as to expose the teeth of the saw blade.
While this blade guard mechanism achieves its intended objective, it suffers from certain deficiencies that reduce its utility. For example, as large circular saws require an accordingly large and heavy lower blade guard, the weight of the guard may cause spontaneous rotation of the blade from the closed position, depending on the angle of the saw relative to the horizontal. If an extension spring with large tensile force is used in order to prevent such inadvertent rotation, stronger resistance to rotation will be felt when the operator abuts the blade guard against the workpiece for retraction, resulting in poorer handling comfort of the tool.